Hard metal alloys and process of making the same



Patented Feb. 6, 1940 UNITED STATES PATENT orrica HARD MIETAL ALLOYS ANDPROCESS OF MAKING THE SAME No Drawing. Application May 5, 1988, SerialNo. 206,171

18 Claims.

The present invention relates to hard metal.

alloys, and it particularly relates to the alloys including refractorymetal carbides which may be utilized for making various types of cuttingtools, wear-resisting implements, and so forth.

In the co-pending applications Serial No. 93,717, filed July 29, 1936,Serial No. 93,733, filed July 31, 1936, and Serial No. 93,734, filedJuly 31, 1936, there are disclosed hard metal alloys in which finelydivided particles of refractory metal carbides, preferably tungstencarbides or carbides of other refractory metals, such as titanium,tantalum, vanadium, thorium, molybdenum, uranium, columbium, andchromium, are encased in relatively thin casings or coatings of cobalt,nickel or iron and are cemented together by said casing or coatings intoa compact mass.

According to the preferred method of making these alloys, the finelydivided carbides, whether 20 of tungsten or other refractory metals, orthe finely divided metals themselves and carbon, having a finenessbetween 150 and 400 mesh, are sprinkled into a relatively concentratedsolution of a cobalt, nickel or iron organic or inorganic acid salt orinto a slurry of insoluble compounds of these metals with stirring.

The preferred cobalt, nickel or iron salts are the organic water solublesalts, such as the acetates, formates, lactates, rather than thenitrates,

0 chlorides or sulphates.

The solution containing the finely divided refractory metal carbide, orthe mixture of the refractory metal itself and carbon, is evaporated todryness with continued stirring followed by reduction of the pulverizeddry mass in a hydrogen atmosphere. After reduction in hydrogen, thealloy produced is compacted and sintered produce the final hard metalalloy.

Similarly to said co-pending applications, it is among the objects ofthe present invention to prepare an improved hard metal alloy at lowcost and of high quality in respect to strength, hardness and density,which may be made of uniform quality from batch to batch, and which willhave a sufficient degree of toughness and density to enable its wideutilization in connection with wear-resisting implements, cutting tools,contact points, and so forth.

Other objects will be obvious and will appear.

mixtures of at'least three refractory metals and carbon.

It is also preferred in certain cases to use mixtures of coating metalsby placing at least two coating metal salts in the solution, as forexample, cobalt and iron salts, or nickel and iron salts, or all threesalts.

Among the preferred refractory metal alloys are tungsten carbide, whichshould constitute a major proportion of the carbides present, tantalumcarbide, which may be present in lesser proportion than the tungstencarbide, and at least one or more of the following carbides in minorproportion: vanadium carbide, thorium carbide. molybdenum carbide,uranium carbide, columbium carbide, and chromium carbide.

These carbides are usually best prepared by obtaining the finely dividedmetal in pure condition, the metal being preferably prepared byreduction in a hydrogen atmosphere in an electric furnace. These finelydivided refractory metals, separately or as mixtures, are preferablycarburized by heating them with finely divided carbon, sugar carbonbeing preferred, in a reducing atmosphere in an electric furnace, whichreducing atmosphere may desirably include hydro-carbon gases or vaporsof carbon compounds, such as acetylene, ethylene, methane, acetaldehyde,allyl alcohol, and so forth. These finely divided carbides may then bemixed together in the desired proportions to produce the required amountof refractory metals in the final hard metal alloy.

Amoung the preferred proportions are between 1% to of titanium,vanadium, or chromium carbide, between 58% to 70% of tungsten carbide,between 10% to 30% of tantalum carbide.

Another satisfactory proportion is 2% to 8% titanium or chromiumcarbide, between 60% to 68% of tungsten carbide, between 15% to oftantalum carbide and between 1 to 2 of vanadium carbide.

A less preferred proportion is about 1% to 7% of titanium carbide, about/2% to 2% of chromium carbide, and about 79% to 89% of a mixture'oftungsten and tantalum carbides.

It is also possible to use the proportion of about 1% to 3% of chromiumcarbide, about 29% to 39% of tungsten carbide, and about 48% to 58% oftantalum carbide.

In all cases it is desirable to include, in addition to the tungstencarbide, at least one carbide selected from the group consisting ofchromium carbide, titanium carbide, thorium carbide and vanadiumcarbide, and usually it is also desired to include tantalum carbide.

Generally, the preferred proportions are between to 10% of these threecarbides, taken singly or in combination, in addition to the tunasten ortantalum carbides, which may be used in equal proportions or with thetantalum carbide being present in the proportion of from 10% to 25% ofthe total mixture of carbides.

It has been found particularly desirable to combine these mixtures of atleast three carbides, or at least tungsten carbide together withtitanium, vanadium and/or chromium carbide, with a saturated solutioncontaining equally molecular proportions of at least two water solublesalts of cobalt, iron and/or nickel. By using a combination of cobaltand nickel or cobalt and iron, or nickel and iron, or all three, it ispossible to obtain a satisfactory hard metal with as little as 1% to 5%of coating metal.

Desirably, the salt content of the solution may consist of 50% each ofcobalt and nickel acetates or formates, or 33 /3% each of the organicsalts of iron, cobalt and nickel. At the same time the carbides areadded to the concentrated or saturated aqueous solution of the cobalt,iron and nickel salts, it is also possible to add finely dividedrefractory metals such as tungsten, titanium, vanadium, chromium,tantalum and so forth, together with finely .divided carbon, and also incertain instances it is possible to add finely divided cobalt or nickeldirectly to the solution before evaporation to dryness or after it hasbeen partly evaporated to dryness.

In the preferred procedure described in said copending applications, thepulverized and finely divided carbide mixture is added to a concentratedsolution of cobalt and nickel acetates.

Although the cobalt and nickel salts may be in complete solution incertain instances, the solution may carry suspended'particles of.cobalt, nickel or iron salts, or even the oxides or hydroxides of thesemetals.

The proportioning of the refractory metal, of the additional metal suchas cobalt, nickel or iron, and of the carbon, is preferably such thatthe refractory metal will constitute between about 88% to 90% of thealloy; while the additional metal will constitute between about 10% and11% of the alloy, or in some few instances more than 25% of the alloy;and the carbon will constitute up to 2% to 3% of. the alloy, and even upto 10% to 15% in certain instances.

In preparing the alloy from the carbide mixture and solution of thecobalt and nickel acetate, the finely divided carbides are mixed ormilled together and are then sprinkled into the cobalt and nickelacetate solution. The liquid is evaporated away with stirring until adry solid mass is obtained. This solid mass may then be finely groundwithout decomposition of the cobalt and nickel salts and then subjectedto reduction, most desirably in an electric furnace in ahydrogenatmosphere. After this reduction operation has been completedthe resultant mass may be formed or pressed to desired shapes and. thensintered to form the finished article ready for commercial use incutting tools, drawing dies, electrical contact points, wear-resistingparts, and so forth.

It is obvious, of course, that it is also possible to utilize ironacetate, formate or lactate in addition to the cobalt and nickelacetates, or to substitute iron acetate either for the cobalt or nickelacetates.

It is also possible to utilize mixtures of different salts such ascobalt acetateand imn formate. or

anaapsa double salts containing cobalt, nickel and iron, such as varioussoluble ammonia derivatives or cyanide derivatives. Certain cyanide andammonia derivatives are particularly helpful in that they form areducing mixture which produces a hard metal alloy of particularly high.quality. These compound salts including ammonia or cyanide groups andalso including copper, iron or nickel, may replace part or all of thewater soluble organic acid salts, although it is only usually desirableto utilize them in amounts up to about,1% to 50% of the organic acidsalts.

The following are several typical examples of carbide mixtures which maybe prepared for incorporation with the cobalt and nickel salt solution,said carbides being preferably produced by reduction and/orcarburization' in a hydrogen atmosphere:

Example 1.-In parts by weight: 5 of. titanium carbide, 63 of tungstencarbide, 20 of tantalum carbide, and 2 of vanadium carbide.

Example 2.--In parts by weight: 4 of titanium carbide, l of chromiumcarbide, and 84 of tungsten carbide.

Exampl 3.-In parts by weight: 2 of chromium carbide, 35 of tungstencarbide, and 53 of tantalum carbide.

Example 4.--'In parts by weight: 38 of titanium carbide, 470 of tungstencarbide, of tantalum carbide, and 15 of. vanadium carbide.

Example 5.'In parts by weight: 3 of chromium carbide, 5 of titaniumcarbide, 5 of thorium carbide, 10 of molybdenum carbide, 20 of tungstencarbide, and 20 of tantalum carbide.

Example 6.In parts by weight: 30 of titanium carbide, 8 of chromiumcarbide, and 636 of tung sten carbide.

Example 7.In parts by weight: 15 of chromium carbide, 260 of tungstencarbide, and 400 of tantalum carbide.

Example 8.--In parts by weight: 1 each of chromium, vanadium, titaniumand thorium carbides, 10 of tantalum carbide, and 20 of tungstencarbide.

Example 9.-In' parts by weight: 10 of chromium carbide, 10 of vanadiumcarbide, and 50 of tantalum carbide.

Example 10.--In parts by weight: 10 of molyb denum carbide, 20 oftantalum carbide, and 50 of tungsten carbide.

In each case these carbides have been preferably prepared by carburizingthe finely divided, pure metal with sugar carbon in a hydrogenatmosphere for two hours at a temperature of 1200 C. to 1600 C. -Themetal powders may be separately carburized or they maybe mixed to getherbefore carburization. These metal powders after carburization are milledfor a couple of days, preferably without balls, to give a finely dividedmixture having a fineness exceeding 180 mesh.

According to one desirableprocess of combination, the milled carbidemixture of Examples 1 to 10 is sieved through a 180 mesh screen or sieveand then sprinkled into a solution of 3'70 parts by weight of equalparts cobalt and nickel acetates in 1,000 parts by weight of water.

or course, either the cobalt or nickel may be replaced in part or wholeby equivalent quantities of iron salts. The solution containingthecobalt and nickel acetates is then evaporated to dryness with constantstirring and the residue is dried for about ten hours and thenthoroughly pulverized so that it may be bolted through a 180 meshscreen.

This powder is then loaded into nickel boats and reduced in a hydrogenatmosphere in an electric furnace according to the following schedule:

Held A hour at 20 volts Held 1% hours at 50 volts Held M hour at 70volts Held 4 hour at volts Held 1% hours at volts The temperature thenreaches about 600 C., which is maintained until reduction is complete.

The boats are then pushed into the cooler and allowed approximatelyfifteen minutes to cool. The final product, which is in the form of avery fine powder, is then formed under pressure to the desired shape.The formed pieces are then placed in carbon tubes and heated in ahydrogen atmosphere in an electric furnace to approximately 1450 C. forthirty minutes or longer, dependent upon the size of the pieces. Thetubes are then pushed into the cooler and when cold they are withdrawn.

Although the high temperature treatments, namely the carburizing, thereduction, and the sintering, are carried out in reducing atmospheres,it has been found most suitable to carry out the carburizing in ahydrocarbon atmosphere, while the reduction and sintering operations arecarried out in a reducing atmosphere, preferably of hydrogen.

Many other changes could be efiected in the particular features ofprocess treatment disclosed, and in specific details thereof, withoutsubstantially departing from the invention intended to be defined in theclaims, the specific description herein merely serving to illustratecertain elements by which, in one embodiment, the spirit of theinvention may be efi'ectuated.

I claim as my invention:

1. A process of preparing hard metal alloys which comprises combining afinely divided mixture of at least three refractory metal carbides andthen combining this mixture with a water solution of an organic salt ofan additional metal selected from the group consisting of iron, nickeland cobalt, said water solution being concentrated and being evaporateddown to dryness while continually stirring, the dry material beingpulverized and sifted and then reduced in a reducing atmosphere, atleast two of said refractory metal carbides consisting of tungstencarbide and tantalum carbide and the other refractory metal carbidebeing selected from the group consisting of vanadium carbide, thoriumcarbide, molybdenum carbide, uranium carbide, columbium carbide, andchromium carbide.

2. A process of preparing refractory metal alloys which comprisescombining a mixture of at least three finely divided carbides ofrefractory metals with a water solution of an organic acid salt ofcobalt, said water solution being concentrated and being evaporated downto dryness while continually stirring, the dry material being pulverizedand sifted and then reduced in a reducing atmosphere, at least two ofsaid refractory metal carbides consisting of tungsten carbide andtantalum carbide and the other refractory metal carbide being selectedfrom the group consisting of vanadium carbide, thorium carbide,molybdenum carbide, uranium carbide, columbium carbide, and chromiumcarbide.

3. A process of preparing hard metal alloys which comprises combining amixture of tungsten, tantalum and vanadium carbides with a watersolution of a double ammonia salt of an additional metal selected fromthe group consists ing of cobalt and nickel, said water solution beingconcentrated and being evaporated down to dryness while subjected tocontinuous stirring, the dry material being pulverized and sifted andthen reduced in a reducing atmosphere.

4. A process of preparing hard metal alloys which comprises combining amixture of tungsten, tantalum and chromium carbides with a watersolution of an organic acid salt of nickel, said water solution beingconcentrated and being evaporated down to dryness while subjected tocontinuous stirring, the dry material being pulverized and sifted andthen reduced in a reducing atmosphere.

5. A process of preparing hard metal alloys which comprises carburizinga mixture of at least three refractory metals, and then combining themixture with a water solution of at least two organic acid saltsselected from the group consisting of the salts of iron, nickel andcobalt, said water solution being concentrated and being evaporated downto dryness while subjected to continuous stirring, the dry materialbeing pulverized and sifted and then reduced-in a reducing atmosphere,at least two of said refractory metal carbides consisting of tungstencarbide and tantalum carbide and the other refractory metal carbidebeing selected from the group consisting of vanadium carbide, thoriumcarbide, molybdenum carbide, uranium carbide, columbium carbide, andchromium carbide.

6. A process of preparing hard metal alloys which comprises carburizingtungsten, tantalum and an additional refractory metal selected from thegroup consisting of titanium, thorium, chromium, molybdenum, vanadium,columbium, and uranium, with sugar carbon, milling the carbides, siftingthe carbides through a 180 mesh screen, and combining the carbides witha water solution of an organic acid salt of cobalt, said water solutionbeing concentrated and being evaporated down to dryness while subjectedto continuous stirring, the dry material being pulverized and sifted andthen reduced in a reducing atmosphere.

7. A process of preparing hard metal alloys which comprises millingtogether carbides of tungsten, tantalum and an additional refractorymetal selected from the group consisting of titanium, thorium, chromium,molybdenum, vanadium, columbium, and uranium, sifting the carbidesthrough a 180 mesh screen, and combining the carbides with cobalt, saidcombination being effected by sprinkling the sifted carbides into aconcentrated solution of cobalt acetate, evaporating to dryness withagitation, reducing the dried mixture and sintering.

8. A method of making hard metal alloys which comprises combiningtogether at least three finely divided refractory metal carbidesselected from the group consisting of titanium, tantalum, tungsten,chromium, uranium, molybdenum, thorium, columbium, and vanadium, andcombining said carbides with a water solution of a salt selected fromthe group consisting of the salts of iron nickel and cobalt, said watersolution being concentrated and being evaporated down to dryness whilesubjected to continuous stirring, the dry material being pulverized andsifted and then reduced in a reducing atmosphere. 9. A method of makinghard metal alloys whieh comprises combining together at least threefinely divided refractory metal carbides selected from the groupconsisting of titanium, tantalum,

tungsten, chromium, uranium, molybdenum, columbium, thorium, vanadium,and sprinkling said carbides into a concentrated salt solution, saidsalt being selected from the group consisting of the salts of iron,nickel and cobalt, evaporating said solution to dryness with agitation,powdering, reducing the powder in a hydrogen atmosphere, forming thereduced powder, and sintering.

10. A process of producing refractory metal alloys which comprisescombining together at least three finely divided refractory metalcarbides, and

then combining this mixture with a water solution of the double cyanidesalts of cobalt and nickel, said water solution being concentrated andbeing evaporated down to dryness while subjectedto continuous stirring,the dry material be- 1% to 10% of at least one carbide selected from thegroup consisting of titanium carbide, molybdenum carbide, vanadiumcarbide, uranium carbide and chromium carbide, about 58% to 70% oftungsten carbide, about 10% to 25% of tantalum carbide, and about 5% to15% of an additional metal selected from the group consisting of cobalt,iron and nickel, each of the carbide particles being encased in andcemented together by a coating of said additional metal, said alloybeing prepared by mixing the carbides with a salt solution of theencasing metal followed by even-- orating, drying, pulverizing,reducing, compressing and sintering.

12. A hard metal alloy consisting of about 2% to 8% of titanium carbide,about 60% to 68% of tungsten carbide, about 15% to 25% of tantalumcarbide, about 1 to 2 of vanadium carbide, and the residue additionalmetal from the group consisting of cobalt, iron and nickel, each of thecarbide particles being encased in and cemented together by a coating ofsaid additional metahsaicl alloy being prepared by mixing the carbideswith a salt solution of the encasing metal, followed by evaporating,drying, pulverizing, reducing, compressing and sintering.

13. A hard metal alloy comprising about 1% to 7% of titanium carbideabout /2% to 2% of chromium carbide, about 79% to 89% of tungsten andtantalum carbides, and the residue be- -ing an additional metal selectedfrom the group consisting of cobalt, iron and nickel, each of thecarbide particles being encased in and cemented together by a coating ofsaid additional metal, said alloy being prepared by mixing the carbideswith a salt solution of the encasing metal, followed by evaporating,drying, pulverizing, reducing, compressing and sintering.

14. A hard metal alloy comprising about 1% to 3% of chromium carbide,about 29% to 39% of tungsten carbide, and about 48% to 58% of tantalumcarbide, and the residue in additional metal selected from the groupconsisting of nickel, iron and cobalt, each of the carbide particlesbeing encased in and cemented together by a coating of said additionalmetal, said alloy being prepared by mixing the carbides with a saltsolution of the encasing metal, followedby evaporating, drying,pulverizing, reducing, compressing and sintering.

15. A hard metal alloy comprising about 90% oi a mixture of at least twohard metal carbides including tantalum and tungsten carbides, and about10% of a mixture of nickel and cobalt, the particles of the carbidebeing each encased in and cemented together by a coating of nickel andcobalt, said alloy being prepared by mixing the carbides with a saltsolution of'the encasing metal, followed by evaporating, drying,pulverizing, reducing, compressing and sintering.

16. A hard metal alloy comprising about 90% of a mixture of at least twohard metal carbides including tantalum and tungsten carbides, and about10% of a mixture of nickel, iron and cobalt, the carbide particles beingeach encased in and cemented together by said last mentioned mixture,said alloy being prepared by mixing the carbides with a salt solution ofthe encasing metal mixture, followed by evaporating, drying,pulverizing, reducing, compressing and sintering.

17. A process of producing a hard metal alloy which comprisesevaporating a slurry containing finely divided cobalt and nickelacetates and at least one hard metal carbide including tungsten carbide,reducing the mixture, forming and sintering. the carbide particles beingeach encased by cobalt acetate before reduction.

18. A hard metal alloy consisting of finely divided tungsten, tantalumand chromium carbides, the particles of which are each encased in, andcemented together by, a coating of an additional metal selected from thegroup consisting of iron, cobalt and nickel, said alloy being preparedby mixing the finely divided tungsten and tantalum carbides with asolution of a water soluble salt of the additional metal to form aslurry, followed by reduction to dryness with constant' agitation,reduction of the dried mixture in hydrogen, and sintering.

HENRY N. PADOWICZ.

